The present invention relates to the art of railway maintenance vehicles and, more particularly, to an improvement in connection with such vehicles of the character having flanged rail engaging wheels and ground engaging tires enabling selective rail and ground support for the vehicle.
Railway maintenance vehicles having both rail and ground support capabilities with respect to maintenance equipment such as dump trucks, cranes, and the like, have been provided heretofore. Such vehicles generally include a frame assembly supporting drivable ground engaging pneumatic tires to enable displacement of the vehicle along a roadway or the like and into position relative to railway rails, and to provide ground support for the vehicle and maintenance equipment during use thereof at a given site along a railway. The ground engaging tires are also used to move the vehicle along the railway within an area in which maintenance is being performed. Such vehicles further include flanged rail engaging wheels supported on the frame assembly for displacement relative thereto between a first position in which the wheels are elevated from engagement with the underlying rails, when the frame assembly and maintenance equipment are ground supported by the tires, and a second position in which the railway wheels engage the rails and elevate the frame assembly and maintenance equipment so as to support the ground engaging tires in suspension above ground. In the latter position the wheels primarily function to facilitate transportation of the vehicle along a railway such as between different areas or locations at which maintenance is to be performed. However, depending on the type of maintenance equipment associated with the vehicle, maintenance work can be performed with the wheels in the second position. The flanged rail engaging wheels are provided in pairs at opposite ends of the frame assembly and, in certain maintenance vehicles, each pair of wheels is supported for displacement relative to the frame assembly whereas, in other vehicles, the wheels are supported for individual displacement relative to the frame assembly.
Railway maintenance equipment of the foregoing character has utility in connection with performing numerous railway maintenance and maintenance related operations such as, for example, rail laying, excavating laterally of railway tracks, and the elevating and lowering of loads such as railway ties, cars, rails and track laying or maintenance equipment and supplies. In connection with these and other maintenance operations, it will be appreciated that considerable lateral or side thrust forces and rocking motions are imposed on the maintenance equipment, such as by the lifting and dropping of heavy loads. Thus, many maintenance operations cannot be performed with the equipment supported on the rails by the flanged wheels in that the narrow wheel base thereof promotes tilting of the vehicle which can result in turning over of the vehicle. Further, in this respect, rocking movement can and does cause derailment of the vehicle when so supported.
While the foregoing potential problems are reduced to some extent by performing maintenance with the flanged wheels elevated and the equipment supported laterally outwardly of the rails by the ground engaging tires, such side thrust and rocking motions still often result in lateral displacement of the vehicle and thus the elevated rail engaging wheels so that the latter are out of alignment with the rails when it is desired to elevate the maintenance vehicle for transportation along the rails on the rail engaging wheels. Lateral misalignment between the railway wheels and underlying rails as the result of lateral displacement of the maintenance equipment relative to the railway is a frequent occurrence and requires a time consuming operation of the maintenance vehicle to regain the desired alignment. Accordingly, a considerable amount of useful time is generally lost in having to periodically realign the vehicle during maintenance operation thereof. Such lateral displacement and misalignment result in excessive wear and damage to the tires. When it is considered that the latter cost about one-thousand dollars each, it will be appreciated that the cost of vehicle maintenance is undesirably high. Still further, such misalignment, or an undesired lateral tilting of the vehicle, can also occur as the result of variations in the level of the ground or railway ties underlying the vehicle tires. More importantly, such side thrust and motion can alone, or together with tilting as a result of uneven elevation conditions along the railway, cause turning over of the maintenance vehicle. It will be appreciated of course that over-turning of the maintenance vehicle is both dangerous to the operator and workmen along the railway and, at a minimum, results in considerable damage to the equipment.